Afterburner igniter



May 12, 1959 w. F. HEMLOCK 2,885,857

AFTERBURNER IGNITER Filed Oct. l1, 1956 ffl/62.571116 :Ej- E INVENTOR.

Mawr "Y I Jni1fd-l Sere Patent L0 2,385,851 AmRnuRNER IGNmzR Application October 11, 1956, Serial No. 615,439 4 Clalins. (Cl. 6039.28)-

This invention relates to afterburner igniters and, more particularly, to an afterburner igniter that repeatedly supplies fuel until ignition occurs within the'afterburner.

An object of this invention is to provide an ignter for an afterburner that automatically supplies fuel for igniting until combustion occurs in the afterburner.

Another object of this invention is to provide an igniter that is notactuated untilthe exhaust nozzle is open,

Other objects of this invention will be readily perceived from the following description.

. This invention relates to a jet engine having a turbine and afterburner means with a control system for regulating the supply of fuel to the engine 4for igniting the afterburner means. This control system includes a pump to supply fuel to the engine, means to drive the pump, means to supply fuel to the pump, and means responsive to the turbine discharge pressure to control the drive means and the supply means.

The attached drawing illustrates a preferred embodiment of the invention, in which Fig. l is a schematic view of a portion of a jet engine embodying the present invention;

Fig. 2 is a sectional view of the fuel pump housing of the present invention; and

Fig. 3 is a diagrammatic view of the electric circuit of the present invention with the pressure control apparatus shown in section.

- Referring to the drawing and particularly Fig. 1, there is shown a portion of a jet engine having a combustion chamber section 11, a turbine section 12, and an afterburner section 14. The afterburner section 14 has an exhaust nozzle 15 at the end thereof which is controlled by suitable movable members 16,' which are commonly known as eyelids These movable members or eyelids 16 "are moved together or-apart'to vary'the area of the exhaust nozzle 15 and, thus, varyl the thrust from the jet engine 10. These members 16 are moved apart when it is desired toemploy the afterburner 14 to 'add thrust to the jet engine 10. This is due to the fact that the volume of hot gases passing through the exhaust nozzle 15 increases when the afterburner is being employed and a larger exhaust' nozzle area is therefore required.

Fuel is supplied to the jet engine 10 for igniting the afterburner by a fuel pump having a housing 17. In the preferred embodiment, the fuel is supplied to the combustion chamber 11 of the jet engine 10 through pipes 18 and 19. The combustion chamber 11 consists of the wellknown burner can arrangement and the pipes 18 and 19 communicate with cans, which are preferably oppositely disposed from each other. The fuel supplied to the combustion chamber 11 for igniting the afterburner 14 produces a ame in the combustion chamber 11 that passes through the turbine 12 into the afterburner 14 of the jet engine 10. While the fuel for igniting the afterburner 14 is shown being supplied to the combustion chamber 11, it will be understood that this fuel could be supplied to the afterburner 14, if desired.

The fuel pump housing 17 includes a pair of chambers 2,885,857 Patented May `12, 195.9

20 and 21 in which a piston member 22 is movable. The piston member 22 is symmetrical and has a central driven portion 23 with an enlarged portion 24 on each side thereof. A reduced portion 25 extends from each of the portions 24 and terminates in an enlarged portion 26 that substantially lits the chambers or cylinders 20 and 21. The housing 17 has a supply passage 27 connected to a suitable fuel supply source (not shown) and subject to the pressure of the fuel metered to the afterburner 14. The ow of fuel through the supply passage 27 is controlled by a valve 28 disposed therein. The supply passage 27 has a branch 29 connected to the chamber 20 and a branch 30 connected to the chamber 21. A passage 31 in the fuel pump housing 17 connects the chamber 20 to the combustion chamber 11 through the pipe 18. A passage 32 in the fuel pump housing 17 provides communication between the chamber 21 and the combustion chamber 11 through the pipe 19.

The piston member 22 is driven by a reversing motor 33 through a gear 34, which meshes with teeth on the piston member 22. The reversing motor 33 is disposed in an electric circuit connected to a power supply 35 and energized by closing of a switch 36. A solenoid 37, which controls movement of the valve 28, is in parallel with the reversing motor 33 and is energized whenever the reversing motor 33 is energized by closing of the switch 36. The switch 36 is connected to a member 38 having its other end secured to a diaphragm 39, which is movable' within a housing 40. The diaphragm 39 divides the housing 40 into chambers 41 and 42 sealed from each other by the diaphragm. The chamber 41 is maintained at the discharge pressure of the turbine 12 through a tube 43 while the chamber 42 is exposed to the inlet pressure of the turbine 12 through a tube 44. Resilient means such as springs 45 and 46 are disposed within the chambers 41 and 42, respectively to position the diaphragm 39 in a neutral position.

Thus, when the members 16 have reduced the area of the exhaust nozzle 15 due to the afterburner 14 not operating, the diaphragm 39 retains the position shown in Fig. 3 due to the pressure at the outlet of the turbine existing in the chamber 41 of a housing 40 and the inlet pressure of the turbine 12 existing in the chamber 42. When it is desired to employ the afterburner 14, the eyelids 16 are moved apart. This, of course, produces a decrease in the turbine discharge pressure and the pressure differential between the inlet and outlet pressures of the turbine 12 results in the diaphragm 39 moving to the left, as viewed in Fig. 3, to close the switch 36 to energize the electrical circuit. When the electrical circuit is energized, the solenoid 37 opens the valve 28 and fuel is supplied through the passage 27 to the chambers 20 and 21 while the reversing motor 33 drives the piston member 22. This results in fuel being pumped from one of the chambers 20 or 21 through its passage 31 or 32 to the jet engine 10 while fuel is supplied to the other of the chambers 20 or 21 through the passage 27. When the piston member 22 reaches the end of its stroke, the reversing motor 33 then drives the piston 22 in the opposite direction to force fuel from the chamber that was previously supplied while fuel is now supplied to the chamber from which fuel had been pumped. One method of reversing the motor is to provide a switch that reverses the polarity of ,the motor when the piston member 22 reaches the end of its stroke.

As seen in Figure 3 the centrally driven portion 23 actuates a downwardly extending actuating arm 23EL projecting through an elongated slot 23b and disposed to engage and close a normally open Microswitch 23c at one end of its reciprocation and engage and open a normally closed Microswitch 23d at the other end of its reciprocation. A relay 23e is provided which is spring stressed upld" wardly by thespring 231' whensolenoid coill 23.g is deenergized by the opening of the normally closed Microswitch 23d. The relay contacts a, a' and a reverse the directions Ofcurrent'flow in theeld coil 33hof the reversing'motor 33;

When the arm 232t is movedin one directionit closes Microswitch 23c and the relay is pulled downby solenoid 23g closing contacts a and a effecting currentflow in the motor field coil 33h in one .direction causing the motor to actuate the gear 34 and shift the piston member 22 throughthe rack on the portion 23'to the right. Circuit through contacts b andb providingaholding circuit maintainingsolenoid coil 23S energized until the arm 23u' is moved by the-part 23 and strikes-and .opensthef normally closed Microswitch 2?d which breaks .the'holding` circuit to'thesolenoid 23g andthe-,spring Y235 -vraises vthe relay arms! to` engage thecontacts a, a,.thusreversing1the: current vflow in thea-field coi1=33l and .reversing therdirer:

tiouroffrotation ofthe motor 33. As'the arm :231a isimoved" to the left. the normally closed' Microswitch 23dv closes: and the motor continues to rotate untilV the' arm` 23`en gagesand closes the normallyopen'vMicroswitchV 23C- reversing the'current ow in the eld coil 33h and vreversing the motor 33 as before'described. This continuesuntil the control switch 36 is opened, disconnecting the power supply.

This arrangement is an old well known limit switch motor reversing circuit and the details thereof' form no part of the invention.

This cycling process is continueduntil ignition occurs in the afterburner 14. At this time, the discharge pressure of the turbine 12 rises and exerts a force within the chamber 41 sucient to open the switch 36. This stops movement of the piston member 22 since it deenergizes the reversing motor 33 and also closesthe valve 28 to prevent the supply of fuel through the passage 27 as the solenoid 37 is also deenergized. If any fuel leaks past the enlarged portions 24 of the piston member 22, itiiows from the housing 17 through a drain 47. Itwill be seen that the present invention repeatedly supplies fuel for igniting the afterburner 14until such ignition'occurs.

An advantage ofthe present invention is that it eliminates the necessity of using hot compressor bleed air for igniter actuation and thereby avoids problems of sealing and fuel coking. Another advantage of this invention is the safety precaution of requiring the exhaust nozzle to open before igniter fuel is injected into the jet engine. A further advantage of this invention is that it eliminates the need of actuating the throttle if the rst fuel squirt fails to'produce combustion in the afterburner.

For purposes of exempliiication, a particular embodi' ment of the invention has beenshown and described according tothe best present understanding thereof. How ever, .it will be apparent that changes and modications in the arrangement and construction of the parts thereof may be resorted to without departing from the true spirit and scope of the invention.

I claim:

1. In a jet engine having a turbine and lafterburner means, a control system for regulating the supply offuel to the engine for igniting the afterburner means including a fuel pump, said pump including a housing having two chambers therein, piston means movable within each of the chambers, means to supply fuel to each of the chambers, reversing meansconnected lto the-pistonrneans to` drive the piston means to pump the tfuel from lone' of 'the chamberstotheienginewhile fuelis supplied" to the other of the chambers, said reversing means then driving the piston means to pump fuel from the other chamber while fuel is supplied to the one chamber, and means responsive to the turbine discharge pressure to control the reversing means and the supply means.

2. In a jet engine having" al turbine and afterburner means, a control'systemzforfregulatinggthessupply of fuel to the engine for igniting the afterburner means including a fuel pump, said pump including a housing having'two' chambers therein, said housing having., a.supply passage therein connected to each of the chambers, .means tocontrol thel ilow of fuel?, throught the?y supply' passage;l said housing having apassage from each ofthe chambers to the engine, a piston mechanism' movable within the chambers to alternately pump fluid from one of the chambers through its passage to the engine while fuel is admitted to the other ofthe. chamberszthroughtberisupply. passage andl viceV versa, an'electricireversigimotorfconnected toy the piston mechanism4 to:` drive.l thepiston meclxanism,` electrical :meansto control .the owcontrolrmeans in the supply passage, and .means'responsive .to turbine-discharge pressure to energize the motor andthe electricalmeans.

3. In a jet engine havingaazturbine and afterburner means, a control'system for regulating the supply of fuel to the engine forigniting the'afterburner means including a fuel pump, said pump including-,ahousing having two chambers therein, said housingyhaving; asupply; passage therein Yconnected to each lof thechambers; means-to con-- trol the ow of fuel through' thesupply passage, said housing having a passagecfrorneach offthev chambers to the engine; a piston mechanism movable withinthe cham'- bers to alternately pump fluid from'oneofthe chambers through its `:passage to thef-engine -whilelfuel is admitted to the other of the chambers through thesupply passage and vice versa, an electric reversing. motor connected to the piston mechanism to drivevthe piston mechanism. electrical means to control the flow control means inthe supply passage, and means `to :energize the motor and the electrical means in responsetoadecrease from a predetermined turbine discharge pressure and .todeenergize the: motor and the electrical meanslimresponse to a return to the predetermined turbine, discharge pressure.-

4. In a gas turbine power plant having afterburnerV means, the combination of farfuelpump to lsupply` fuel for ignitingthe afterburner means, said fuel pump having twochambers and piston meansy movable inisaid chambers to alternately pump fuel therefrom, means to supply fuel` tov each` of the chambers alternately when the piston meansl isfpumpinggfuel from the-iother 'of the'. chambers, means 'to` drive Lthe ,piston meansfin reverse directions, and' means :responsiveto the turbine dischargepressurc to control the drive means -and-.the'supply means.

References Cited: inthe "file: of `this spatenty UNITED' STATES PATENTS" 2,469,678 Wyman May 10, 1949' 2,470,564- Lawrence, et al. May 17, 1949' 2,643,511'v Briggs- June 30, 1953 2,652,813` StresenReuter et al. Sept. 22,l 1953 2,736,166 Mock- Feb.f2`8,v 1956y FOREIGN PATENTS 660,178 Great Britain..A Oct; 31, 1951 

